In recent years, expectations for a self-luminescent organic EL display using organic EL elements as the next-generation display have been grown. The organic EL display is self-luminescent and displays bright and vivid images. For this reason, the organic EL display has excellent features such as a wide viewing angle and high response speed. Further, because the organic EL display does not need a backlight, a thin display can be made advantageously and easily. Therefore, application of the organic EL display to, for example, TVs having a large display in future has been expected.
The organic EL elements constituting the organic EL display can be formed on the surface of an insulation film on a TFT substrate. Each of the organic EL elements includes a pixel electrode arranged on the insulation film, an organic functional layer containing fluorescent molecules that is arranged on the pixel electrode, and a counter electrode arranged on the organic functional layer.
In recent years, as the organic EL display becomes larger and features higher definition, it becomes more likely that a foreign particle contaminates the pixel electrode when the pixel electrode is formed on the insulation film on the TFT substrate. In the case where a foreign particle contaminates the pixel electrode, when the organic functional layer and the counter electrode are formed over the pixel electrode, the pixel electrode and the counter electrode are electrically connected via the foreign particle. For this reason, when a current is applied to the organic EL element, a short circuit may occur due to the foreign particle. When a short circuit occurs, a current does not pass through the organic functional layer on this pixel electrode. Therefore, the organic functional layer does not emit light, and thus the pixel having the foreign particle becomes a defective pixel. Further, due to a short circuit, the larger amount of current that does not contribute to light emission passes between the pixel electrode and the counter electrode. Accordingly, the efficiency of light emission of the organic EL element is lowered.
In order to overcome the above problem, various methods have been suggested in which, when a foreign particle contaminates the electrode or the like, the pixel electrode or the organic functional layer is repaired by removing this foreign particle (for example, see Patent Literatures 1 and 2).
A repairing method of Patent Literature 1 is shown in FIG. 9. Patent Literature 1 discloses a method of removing foreign particle 2 by placing rotation tool 4 in contact with electrode pad 1 having the foreign particle 2. Rotation tool 4 has roughened grinding surface 3 on the surface of the tip thereof. Patent Literature 1 also suggests removing a foreign particle by releasing an abrasive liquid from an abrasive outlet provided on the tip of the rotation tool and grinding the electrode pad with the abrasive liquid.
A repairing method of Patent Literature 2 is shown in FIG. 10. Patent Literature 2 discloses repairing a pixel by irradiating foreign particle 2 that has contaminated organic layer 5 of an organic EL element with laser 7 emitted from laser oscillator 6 to remove the foreign particle 2 together with part of the organic layer around the foreign particle 2. Foreign particle 2 is irradiated with laser 7 by focusing laser 7 using objective lens 8 or the like according to the size of the foreign particle.
Other methods for removing a foreign particle are also known: a method in which a foreign particle is electrically isolated by irradiating part of a pixel electrode around the foreign particle with a high energy ray such as laser light (for example, see Patent Literatures 3 to 5), a method in which the organic functional layer of a pixel containing a foreign particle is peeled using an adhesive and the pixel is re-supplied with material ink of the organic functional layer (for example, see Patent Literature 6), a method in which a foreign particle is removed from a pixel by attaching the foreign particle in the pixel to an adhesive tape and peeling the adhesive tape from the pixel (for example, see Patent Literature 7), and a method in which an additional organic EL layer or an insulation layer is formed on a foreign particle in an organic EL layer (for example, see Patent Literature 8).